@article{SF_1980__19_134370,
     author = {F.W. Roush and K.H. Kim},
     title = {The average rank of a product of transformations.},
     journal = {Semigroup forum},
     pages = {79--86},
     publisher = {mathdoc},
     volume = {19},
     year = {1980},
     zbl = {0429.20057},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__19_134370/}
}